gpu: nova-core: register: add support for register arrays

gpu: nova-core: register: add support for register arrays

Having registers that can be interpreted identically in a contiguous I/O
area (or at least, following a given stride) is a common way to organize
registers, and is used by NVIDIA hardware. Thus, add a way to simply and
safely declare such a layout using the register!() macro.

Build-time bound-checking is effective for array accesses performed with
a constant. For cases where the index cannot be known at compile time,
`try_` variants of the accessors are also made available that return
`EINVAL` if the access is out-of-bounds.

Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20250718-nova-regs-v2-17-7b6a762aa1cd@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>